Energy storage is a crucial component of a large number and variety of electronic devices, particularly mobile devices and vehicles, such as electric and hybrid gas-electric vehicles (also “hybrid vehicles” herein). Energy storage devices can be based on a variety of physical effects. For example, electric fields can be employed to store energy in capacitors, and chemical reactions (involving ion motion) can be employed to store energy in batteries. However, energy storage in a capacitor can be limited by the geometry of current devices (e.g., 2-D capacitor plates having limited surface areas) and either a low permittivity or low dielectric breakdown voltage, and batteries can have a slow response time due to the relatively slow ion motion inherent in electrochemical reactions.
There are limitations associated with current batteries. For example, current batteries can have low storage densities due to the relatively low voltage (<5V) resulting from the electrochemical reactions of the ions. In addition, the low mobility of ions in current batteries can lead to slow charge and discharge performance. Furthermore, the reliance of existing batteries on ionic transport causes high degradation rates of the batteries. The performance of battery powered devices, such as hybrid or electric vehicles, can be limited by the low energy stored per weight of batteries used in such vehicles.